Exampro

Question 1

What is the inner layer of an artery?

Answer 1

Endothelium

Question 2

Describe the advantage of having elastic tissue in the wall of an artery

Answer 2

• Elastic tissue allows recoil

- Maintains blood pressure

Question 3

Explain how aerobic respiration in cells leads to a change in the pH of blood plasma.

Answer 3

• Co2 is produced in respiration

- Hydrogen ions produced

Question 4

What is the advantage to tissue cells of a reduction in the affinity of haemoglobin for oxygen when the plasma pH decreases

Answer 4

• Low pH because high rate of respiration
• Cells need more o2
• More 02 released - faster rate

Question 5

Explain the advantage for mice living at high altitude in having a dissociation curve which is to the left of the curve for mice living at low altitude. (2)

Answer 5

• High altitudes have a low partial pressure of o2
• High saturation of Hb with o2 at low partial pressure o2
• So sufficient o2 supplied to cells

Question 6

Suggest why it would be a disadvantage for the curve to be much further to the left (1)

Answer 6

• Difficult to unload/ dissociate o2 (at tissues)

Question 7

Describe how you would calculate cardiac output from heart rate and stroke volume (1)

Answer 7

Cardiac output = heart rate x stroke volume

Question 8

Describe and explain four ways in which the structure of a capillary adapts it for the exchange of substances between blood and the surrounding tissue (4)

Answer 8

• Permeable capillary wall
• Single cell/ thin walls = reduces diffusion distance
• Flattened endothelial cells = reduces diffusion distance
• Small diameter = large SA to volume = short diffusion distance

Question 9

Explain how tissue fluid is formed and how it may be returned to the circulatory system (6)

Answer 9

• Hydrostatic pressure of blood high at arterial end
• Water soluble molecules pass out
• Large molecules remain
• Lowers the water potential = more negative
• Water moves back into venous end of capillary by osmosis
• Lymph system collects any excess tissue fluid which returns to circulatory system

Question 10

The max pressure in the ventricle is much higher than that in the atrium. Explain what causes this (2)

Answer 10

• Ventricle has thick walls/ more muscle

- Contractions are stronger

Question 11

Explain the relationship between the depth of the red colour of the solution and how much haemolysis has taken place (2)

Answer 11

• Red colour is due to haemoglobin

- The more haemoglobin released the more red the solution

Question 12

During treatment in a veterinary surgery, any of the mammals in the figure above may be given an infusion of sodium chloride solution directly into a vein. The concentration of sodium chloride solution used is 0.9% rather than 0.5%, regardless of the species of mammal. Explain the advantage to the vet of using this concentration. (2)

Answer 12

• Won’t cause haemolysis in any of the mammals

- SO cheaper to have one concentration of sodium chloride solution